<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body {
            background-color: #f3f3f3;
        }
        .bgc .one{
            background-color: red;
        }
        .bgc .two{
            background-color: green;
        }
        .bgc .three{
            background-color: transparent;
        }
    </style>
</head>

<body>
    <div class="bgc">
        <div class="one">
            红色背景
        </div>
        <div class="two">
            绿色背景
        </div>
        <div class="three">
            透明背景
        </div>

        </div>
</body>

</html>